This invention relates to an engine control method and apparatus and more particularly to an improved, simplified, highly effective and yet low cost arrangement for such control.
In internal combustion engines, a wide variety of systems and methodology are employed for engine control. Generally, smaller and lower volume engine applications incorporate generally less sophisticated controls than those employed on larger production volume engines such as automotive engines. Even in the small displacement lower production volume engines, for example those used in motorcycles, the engine control can become quite complicated.
For example and as shown in FIG. 1, the spark control for a motorcycle engine is shown schematically. The control arrangement is intended to control the firing of a spark plug 21 associated with an internal combustion engine 22 that powers the motorcycle, which is not shown in this figure, but which may be of a construction as generally shown in FIG. 3. An amplified spark voltage is applied to the spark plug 21 from an ignition coil 23, which, in turn, is controlled by an ignition timing control arrangement, indicated schematically at 24. This timing control arrangement 24 receives the inputs from a number of engine-associated sensors. These include a crankcase rotational speed sensor 25 which may comprise a pulser coil and a throttle position sensor 26, which is coupled to the throttle control mechanism for the engine 22 and inputs a signal to the control 24 indicative of engine load and/or operator demand.
Electrical power is provided to the ignition control circuit 24 from a battery 27 through a main switch 28. This battery power is applied to a power source circuit 29 of the control 24 and specifically to an electronic circuit 31 which may comprise a microprocessor.
The output from the engine speed sensor 25 is transmitted to a rotational speed detector circuit 32, which counts the number of pulses generated in a time period so as to determine the rotational speed of the crankshaft of the engine 22.
This outputs a speed signal N to an ignition timing determining circuit, indicated at 33. In addition, the throttle position sensor 26 inputs a signal to a throttle position detector circuit 34. This detector circuit 34 outputs a signal xe2x80x9caxe2x80x9d to a throttle opening calculating circuit 35. This, in turn, outputs a throttle angle position xcex8 to the ignition timing determination circuit 33.
From these inputs, the ignition timing determining circuit outputs a signal at a time determined from maps contained in a memory of the circuit 31 to an ignition circuit 36 which may be of the capacitor discharge type so as to output an electrical output xe2x80x9cixe2x80x9d to the coil 23 which is stepped up by the coil 23 to a value xe2x80x9cIxe2x80x9d for firing the spark plug 21 in a well-known manner.
FIG. 2 is a graph showing one of the maps which may be incorporated in the circuit 31 and shows how the spark timing is varied in response to engine speed for given load as determined by the throttle opening circuit. There may be a family of such curves so as to vary the ignition timing in response to both throttle position and engine speed.
Rather than using a throttle position sensor, load may be sensed by intake manifold vacuum. Either method, however, requires added sensors, transducers and circuitry.
It has been found that merely using engine speed and load as detected by something such as a throttle position or intake manifold vacuum sensor does not actually provide as good a control as desired. That is, these two factors by themselves may not be sufficient to provide the desired degree of control.
Although systems have been provided for automotive applications wherein more sophisticated controls are employed, this further adds to the cost of the system and does not always provide the optimum results.
There have also been other devices than throttle position sensors or vacuum sensors for sensing intake manifold vacuum for determining engine load. It also has been determined that engine load may be found by comparing engine speed from one revolution to another. However, these systems also tend to be complicated and do not lend themselves particularly low production volume, low cost vehicle applications. They also have the disadvantage of requiring a plurality of different types of sensors.
Other arrangements have been proposed wherein engine speed is measured for less than one complete revolution of the engine and variations from cycle to cycle have been employed to determine engine load. These systems, however, have for the most part, required multiple sensors and also require some delay from the sensed conditions before adjustment is being made.
In the aforenoted co-pending application a system and method is disclosed that measures engine speed for a portion of a revolution and for a complete revolution utilizing a single sensor and makes engine system adjustments in response to the variation of the measured ratios. This permits a more accurate control with a relatively simple system. However, further improvements can be made.
It is desirable to keep the system as simple and as low a cost as possible. The inventors have discovered that cycle to cycle adjustments are not always necessary or even desirable. Also the sensitivity of the system can be effectively varied depending on the type of vehicle to which it is applied.
It is therefore a principle object of this invention to provide a highly effective, simple and low cost engine control device and method.
It is a further object of this invention to provide an engine control device and method that can utilize a relatively simple and compact computer and memory.
This invention is adapted to be embodied in an internal combustion engine control system and a method for operating an engine for controlling a system of the engine. The engine has a driven shaft. A sensor arrangement is associated with the driven shaft for sensing the instantaneous rotational speed of the driven shaft during the rotation of the driven shaft for less than a complete rotation and for sensing the rotational speed of the driven shaft for a complete revolution thereof including the measured less than complete rotation during a first rotation of the driven shaft and for sensing same two rotational speeds of the driven shaft during the immediately succeeding rotation of the driven shaft. A control determines the ratios between the partial and complete revolution measured for each of the two revolutions and the difference between them. The control adjusts the control of the engine system in response to the difference only if the difference is between a pair of predetermined values. In addition the adjustment is only made with certain other parameters to offer further simplification and provide a smoother operation.
In accordance with a first feature of the engine, the other parameter is that adjustment is made only in whole integers to minimize the necessary memory.
In accordance with a second feature of the engine, the other parameter is that the ratio is utilized to make the adjustment only within a predetermined range of the total expected variation range to avoid excessive calculations.
In accordance with a third feature of the invention, the engine powers a vehicle and the other parameter is that the adjustment is made only within a predetermined range of engine loadings to avoid excessive calculations.